1. Technical Field
The present invention relates to an electronic timepiece, and relates more particularly to an electronic timepiece that receives satellite signals transmitted from positioning information satellites such as GPS satellites and acquires current time information.
2. Related Art
The global positioning system (GPS) is a system for determining one's own location, and uses GPS satellites orbiting the Earth. Each GPS satellite has an on-board atomic clock, and each GPS satellite uses the atomic clock to keep time with extremely high precision (referred to as the GPS time or satellite time information). This time information is carried in the satellite signals transmitted by each GPS satellite, and electronic timepieces that receive these satellite signals, acquire the time information, and adjust the internal time of the electronic timepiece are known from the literature. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2005-221449.
Receiving a satellite signal to adjust the internal time requires a relatively large amount of power. The timepiece taught in JP-A-2005-221449, however, receives the satellite signal and adjusts the internal time at a specific time interval regardless of the remaining battery capacity. As a result, receiving a satellite signal may consume significant power to drive the device even though the remaining battery capacity is low, and could shorten the time that the device can be driven, possibility resulting in a sudden system shutdown.